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Dive Dry with Dr. Bill

#461: Pelt-o-Doris

You can call it the Pacific sardine, the California sardine or the California pilchard... or even use its scientific name, Sardinops sagax, but whichever name you choose it will still taste the same. That is unless you order it in olive oil of tomato sauce instead of water. This baitfish is a member of the family Clupeidae which includes the herring, menhaden, pilchards, sardines and shad. They travel in schools ranging in size from hundreds of thousands to millions. These schools often become tightly knit and polarized in the presence of danger. Sometimes other baitfish species like jack mackerel will join the sardine schools. After all, there is strength in numbers.

These small silvery fish are said to reach lengths of 16 inches although they are seldom longer than 9 inches. The single dorsal fin is located over the middle of the body, and the tail fin is forked. They utilize countershading typical of fish that swim in open water. The back is a dark blue or blue-green, turning silvery on the flanks and the belly is white. I never suntan my belly either! One identifying feature is the row of black spots along the middle of the body just above the lateral line. The mouth, which opens directly in front, is large and oblique. However, one way of telling the sardine from the northern anchovy is by the much larger mouth of the latter, often readily observed even at a distance when they are feeding.

The species Sardinops sagax is widely distributed around the globe. Recent genetic studies suggest separate subpecies exist in South Africa, Australia and New Zealand; the NW Pacific and here in the eastern Pacific. On our coast its geographic distribution is variable depending on its abundance. Its total range goes from Kamchatka and SE Alaska to the tip of Baja California, into the Gulf of California (or Sea of Cortez) and down to Guaymas, Mexico. During years when numbers are very low, it may not be seen north of Pt. Conception and the population may be centered off central and southern Baja. This species is very mobile and highly migratory, often traveling more than 600 miles between its feeding and spawning grounds. Studies looking at the history of the species over the last 1,500 years indicate that natural cycles in abundance occur corresponding to changes in climate over periods of about 50-75 years.

The Pacific sardine is a planktivore meaning it feeds on plankton. Schools as massive as theirs require an abundant food supply, which plankton affords thanks to the continual input of energy from the sun. In turn the sardine is eaten by just about everything else: fish including yellowtail, barracuda, bonito, tuna, marlin and sharks; seabirds such as pelicans, cormorants and seagulls; and marine mammals from seals and sea lions to dolphins and whales. On one island in the Gulf of California where an estimated half a million Heermann's gulls and elegant terns nest, they are believed to munch 65 tons of sardines per day!

Humans have been voracious predators of the sardine as well. Although rich in selenium, vitamin B12, calcium, niacin and phosphorous... they are also high in cholesterol. Sardines are caught in purse seines or lampara nets. Only a quarter of the US domestic harvest is consumed here with the rest shipped to Asia, primarily Japan. They are also used for fish oil and for fish meal used to feed certain species of farmed fish... as well as chickens and pigs. It would be far better from an ecological perspective to eat the sardine rather than converting it into other forms of edible flesh due to the loss of available energy in each link in the food chain.

The history of the sardine fishery on the West Coast is illustrative. It began in 1916 due to the nation's need for new food sources during World War I, and expanded rapidly after the War ended. In 1936 the fishery peaked when 700,000 metric tons were harvested out of an estimated total biomass of 3.6 million metric tons. During the 1930s and early 1940s it was the largest fishery in the western hemisphere. About 200 commercial boats fished sardine and they accounted for 25% of all the fish landed in the US.

In 1946 and 1947 the fishery collapsed. Commercial fishers targeted other species like the jack mackerel, and new regulations regarding sardines came into play. In 1965 the harvest was a mere 10,000 metric tons. The new regulations helped the sardine recover in the early 1980s and landings rose to 1.7 million metric tons by 2000, then declined to about 835,000 seven years later. It was the number one fishery in Mexican waters in 2000.

Of course it took a lot of reproducing to bring about the recovery. The size and age at which a sardine is sexually mature depends on factors such as population size, geographic location and water temperature. When densities are low, fish may mature after one year. When high, only some of the two year olds are ready to spawn. Those in the southern part of the range may spawn year-round, while those in the Pacific Northwest may peak from May to July. Spawning occurs in loose schools with the youngest individuals spawning half a dozen times and the oldest up to forty times in a year. Hmmm... I'm old!

The eggs hatch quickly, in about three days. Of course many of them are filtered out of the water by invertebrate plankton feeders and plankton eating fish so "infant mortality" is high. They grow fast, reaching half their maximum length by the end of the first year and 90% of it by four years. Most report their lifespan at 12 to 15 years, but some believe they may live as long as 25 years. However the vast majority of the population never makes it past six years. Ha, just a bunch of kids!

© 2011 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 29, 10:00 AM weekdays and on Charter Communications Cable channel 33 at 7:30 PM on Tuesdays in the Riverside/Norco area. Please help me climb out of self-imposed poverty... buy my DVD's (see this link). Yes, take Dr. Bill home with you... we'll both be glad you did!

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Images of Mulliner's dorid in the Casino Point Dive Park.

This document maintained by Dr. Bill Bushing.
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